Problem: A bag contains 5 red, 6 green, 7 yellow, and 8 blue jelly beans.   A jelly bean is selected at random.  What is the probability that it is blue?
Solution: In total, there are $5+6+7+8=26$ jelly beans in the bag.

Since there are 8 blue jelly beans, the probability of selecting a blue jelly bean is  $$\frac{8}{26}=\boxed{\frac{4}{13}}.$$